The major difference between insulin-dependent diabetes (IDDM) and non-insulin dependent diabetes (NIDDM) is whether or not there is residual beta cell secretory capacity. Individuals with IDDM have absolute insulin deficiency and thus are dependent on exogenous insulin for survival. Omission of daily insulin injection results in ketoacidosis. This project is designed to answer the following hypotheses: 1) Obese individuals with ketosis prone insulin dependent diabetes have absolute insulin deficiency in contrast to obese subjects with NIDDM; 2) IDDM, defined as absolute insulin deficiency, is not always of autoimmune etiology.